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Alarm clock
An alarm clock is a clock that is designed to make a loud sound at a specific time. The primary use of these clocks is to awaken people from their sleep in order to start their days in the mornings, but can also be used for short naps; they are sometimes used for other reminders as well. To stop the sound, a button or handle on the clock needs to be pressed, and some stop automatically after a few minutes if left unattended. A classical analog alarm clock has an extra hand that is used to specify the time at which to activate the alarm. Traditional mechanical alarm clocks have one or two bells that ring, but digital alarm clocks can make other noises. Simple battery-powered alarm clocks make a loud buzzing sound, or other similar noise to wake a sleeper, while novelty alarm clocks can speak, laugh, or sing. Some alarm clocks have radios that start playing at specified times, and are known as clock radios. A progressive alarm clock, still new in the market, can have different alarms for different times (see Next-Generation Alarms). In a mechanical bell-style alarm clock, a mainspring drives a gear that propels a clacker back and forth between two bells or between the sides inside a single bell. In an electric bell-style alarm clock, the bell rings with an electromagnetic circuit and armature that turns the circuit on and off again repeatedly. History In China, a striking clock was devised by the Buddhist monk and inventor Yi Xing (683–727).Joseph Needham, Volume 4, Part 2, pp. 473–5 The Chinese engineers Zhang Sixun and Su Song integrated striking clock mechanisms in astronomical clocks in the 10th and 11th centuries, respectively.Joseph Needham, Volume 4, Part 2, p. 165 The first striking clock outside of China was the water-powered clock tower near the Umayyad Mosque in Damascus, Syria, which struck once every hour. It was constructed by the Arab engineer al-Kaysarani in 1154.Abdel Aziz al-Jaraki (2007), When Ridhwan al-Sa’ati Anteceded Big Ben by More than Six Centuries, Foundation for Science Technology and Civilisation In 1235, an early monumental water-powered alarm clock that "announced the appointed hours of prayer and the time both by day and by night" was completed in the entrance hall of the Mustansiriya Madrasah in Baghdad. From the 14th century, some clock towers in Western Europe were also capable of chiming at a fixed time everyday, the earliest European example described by the Florentine writer Dante Alighieri in 1319.Joseph Needham, Volume 4, Part 2, p. 445 The first mechanical clock, specifically astronomical clock, with an alarm setting mechanism, was designed by Taqi al-Din, of the Ottoman Empire, and described in his 1559 book The Brightest Stars for the Construction of Mechanical Clocks (Al-Kawākib al-durriyya fī wadh' al-bankāmat al-dawriyya). Another mechanical alarm clock was created by Levi Hutchins, of New Hampshire in the United States, in 1787. This device he made only for himself however, and it only rang at 4 AM, in order to wake him for his job. The French inventor Antoine Redier was the first to patent an adjustable mechanical alarm clock, in 1847. Alarm clocks, like almost all other consumer goods in the United States of America, ceased production in the spring of 1942, as the factories which made them were converted over to war work during World War II, but they were one of the first consumer items to resume manufacture for civilian use, in November 1944. By that time, a critical shortage of alarm clocks had developed due to older clocks wearing out or breaking down. Workers were late for, or missed completely, their scheduled shifts in jobs critical to the war effort because "my alarm clock is broken". In a pooling arrangement overseen by the Office of Price Administration, several clock companies were allowed to start producing new clocks, some of which were continuations of pre-war designs, and some of which were new designs, thus becoming among the first "postwar" consumer goods to be made, before the war had even ended. The first radio alarm clock was invented by James F. Reynolds, in the 1940s and another design was also invented by Paul L Schroth Sr. The price of these "emergency" clocks was, however, still strictly regulated by the Office of Price Administration. Modern digital alarm clocks typically feature a radio alarm function and/or beeping or buzzing alarm, allowing a sleeper to awaken to music or news radio rather than harsh noise. Most also offer a "snooze button", a large button on the top that stops the alarm and sets it to ring again at a short time later, most commonly nine minutes. Some alarm clocks also have a "sleep" button, which turns the radio on for a set amount of time (usually around one hour). This is useful for people who like to fall asleep with the radio on. Digital clock radios often use a battery backup to maintain the time in the event of a power outage. Without this feature, digital clocks will reset themselves incorrectly (usually to midnight) when power is restored, causing a failure to trigger the alarm. To solve this issue, some radio clocks (not to be confused with clocks with AM/FM radios) have a feature which sets the time automatically using radio signals, making the clock ready for use right out of the box. See also * Delayed sleep phase syndrome * Digital clock * Light therapy * Timer References Sources * * * External links * Associations with numbers on the Digital Clock * An online alarm clock * An Online Video Alarm clock * An online flash alarm clock Category:Alarms Category:Clocks Category:Sleep